1. Technical Field
The disclosure relates to electrosurgery combined with optical detection of blood, and more particularly the automatic control of the level of electrosurgical energy to be delivered to tissue in accordance with the amount of blood optically detected.
2. Description of the Related Art
Electrosurgery involves the application of radio frequency energy to achieve a tissue effect. An electrosurgical generator is used in surgical procedures to deliver electrical energy to the tissue of a patient. An electrosurgical generator often includes a radio frequency generator and its controls. When an electrode is connected to the generator, the electrode can be used for cutting or coagulating the tissue of a patient with high frequency electrical energy. During normal operation, alternating electrical current from the generator flows between an active electrode and a return electrode by passing through the tissue and bodily fluids of a patient.
The electrical energy usually has its waveform shaped to enhance its ability to cut or coagulate tissue. Different waveforms correspond to different modes of operation of the generator, and each mode gives the surgeon various operating advantages. Modes may include cut, coagulate, a blend thereof, or desiccate. A surgeon can easily select and change the different modes of operation as the surgical procedure progresses.
In each mode of operation, it is important to regulate the electrosurgical energy delivered to the patient to achieve the desired surgical effect. This can be done, for example, by controlling the output energy from the electrosurgical generator for the type of tissue being treated.
Different types of tissues will be encountered as the surgical procedure progresses and each unique tissue requires more or less energy in terms of voltage, current or power as a function of frequently changing tissue impedance and other factors, such as the level of vascularization, i.e., blood flow within the tissue. Therefore, the same tissue will present different load impedance as the tissue is desiccated.
Two conventional types of energy regulation are used in commercial electrosurgical generators. The most common type controls the DC power supply of the generator by limiting the amount of power provided from the AC mains to which the generator is connected. A feedback control loop regulates output voltage by comparing a desired voltage or current with the output voltage or current supplied by the power supply. Another type of power regulation in commercial electrosurgical generators controls the gain of the high-frequency or radio frequency amplifier. A feedback control loop compares the output power supplied from the RF amplifier for adjustment to a desired power level.
U.S. Pat. Nos. 3,964,487; 3,980,085; 4,188,927 and 4,092,986 have circuitry to reduce the output current in accordance with increasing load impedance. In those patents, constant voltage output is maintained and the current is decreased with increasing load impedance.
U.S. Pat. No. 4,126,137 controls the power amplifier of the electrosurgical unit in accord with a non-linear compensation circuit applied to a feedback signal derived from a comparison of the power level reference signal and the mathematical product of two signals including sensed current and voltage in the unit.
U.S. Pat. No. 4,658,819 has an electrosurgical generator which has a microprocessor controller based means for decreasing the output power as a function of changes in tissue impedance.
U.S. Pat. No. 4,727,874 includes an electrosurgical generator with a high frequency pulse width modulated feedback power control wherein each cycle of the generator is regulated in power content by modulating the width of the driving energy pulses.
U.S. Pat. No. 3,601,126 has an electrosurgical generator having a feedback circuit that attempts to maintain the output current at constant amplitude over a wide range of tissue impedances.
None of the aforementioned U.S. patents include optical detection of blood for regulating or controlling the output energy or output waveforms of the electrosurgical generator during different operational modes over a finite patient tissue impedance range. Optical detection of blood during electrosurgery also allows surgeons with color blindness to effectively perform electrosurgery. In a study that was published in 1997, 18 of 40 physicians with color blindness reported difficulties in detecting blood in body products. Spalding, J. Anthony B., “Doctors with inherited colour vision deficiency: their difficulties in clinical work,” Cavonius C R, ed., Colour Vision Deficiencies, XII: Proceeding of the International Research Group for Colour Vision Deficiencies, 1995, Norwell, Mass.: Kluwer Academic Publishers, pages 483-489, 1997.
Accordingly, there exists a need for a method and system for optically detecting blood during electrosurgery and controlling the output energy or output waveforms of an electrosurgical generator in accordance with the amount of blood optically detected.